The most common and most likely answer to this crossword clue is the 12 letter word CATCH-PHRASE
C
A
T
C
H
-
P
H
R
A
S
E
Buddy explains!

The straight part
We know that "Oft-repeated utterance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case oft-repeated utterance = catch-phrase.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CATCH-PHRASE mean?
CATCH-PHRASE noun- A group of words, often originating in popular culture that is spontaneously popularized after widespread repeated use.
- A signature phrase of a particular person or group.